1. Field of the Invention
The present invention relates to a multilayered optical associative memory device or an optical neural network device.
2. Description of the Prior Art
Numerous studies are known which parallelly implement large volume computation problems on a neural network utilizing the parallel property of light. Many optical computers used in those studies employ holograms, for example:
A1. Y. Owechko, "Hybrid optical and electronic associative memory", (U.S. Pat. No. 4,837,843); PA0 A2. Y. Owechko, Optical Computing 90, 10-a-1 (1990); PA0 A3. A. Yariv. et. al., Phys. Lett. 48, (1986) 1114; PA0 A4. Kitayama K., et. al., IJCNN 1989 Vol. 2,465-741 (1989); PA0 A5. E. G. Peak, D. Psaltis, Optical Engineering, Vol. 26, No. 5,428 (1987); PA0 A6. Y. S. Abu-Mostafa, Demetri Psaltis, Sci. Am., Vol. 256, No. 3, PP 66-73 (1987). PA0 B1. Fisher, A. D., "Adaptive Associative-Processing Optical Computing Architectures", (U.S. Pat. No. 4,862,406); PA0 B2. H. J. Caulfield, SPIE, 456,2, Optical Computing (1984); PA0 B3. K. Kyuma, Optical Computing 90,10-A-2 (1990); PA0 B4. N. H. Farhat, et. al., Applied Optics, Vol. 24, No. 10,1469 (1985); PA0 B5. N. Mukohzaka, U.S. patent Ser. Nos. 07/203,909 filed Jun. 8, 1992 now abandoned and 07/204,350 filed Jun. 9, 1992 now abandoned (Associatron).
Use of such holograms, however, leads to the problem that crosstalk might be produced upon multiplexing. This is a problem the devices being integrated and a problem an optical hologram computing system.
To solve these problems, a number of studies to realize an associative memory without use of a hologram have been proposed for example:
These prior techniques however have the following problems. Techniques of B1, B2, B3 and B5 have insufficient associative function because of being a system with a single layer. In technique B3 learning is not taken into consideration; therefore, it can not adapt to changes in environment, which is one of features of a neural network. The B1 technique of requires an electric synchronous circuit which prevents an input from being processed as an intact image (as an optical pattern), because it is combined with an AO element. The technique of B4 also requires some processing by an electric circuit.